We just got back from the 'No Kings' rally, in our case we were down in Laguna Hills (there was no rally in Irvine as they have a rally every Sunday in front of city hall).
There were probably 2,000 to 3,000 people there. It covered the sidewalks, on both sides of the street, for about three city blocks, plus down some of the side streets and in other places where people could gather. And this was just one of probably eight or nine locations in Orange County alone.
There were a lot of people in costume, inspired I guess by what's been happening in Portland for the last week or so.
Note that it was totally peaceful and there were no counter-protestors.
And my 'Gulf of Mexico' T-shirt was a hit, with many people asking if they could take a picture.

OCU